1. Technical Field
The present disclosure relates to a printer that prints by ejecting ink droplets from ink nozzles, and to a printing method.
2. Related Art
In printers that print by ejecting ink from ink nozzles, the ink nozzles can become clogged as a result of moisture evaporating from the ends of the nozzles and ink viscosity increasing in ink nozzles from which ink is not ejected for a particular time or longer. As a result, ink cannot be ejected normally from ink nozzles with a low ejection frequency, and print quality may drop. Ink nozzles becoming clogged can be prevented or corrected, however, by providing a maintenance unit inside the printer and ejecting ink into the maintenance unit in a flushing operation (referred to below as regular flushing). Ink may also be ejected onto the printing paper (referred to below as “onto-paper flushing”) to prevent or resolve ink nozzle clogging.
A drop in throughput is a problem with regular flushing because the printhead must first be moved to the maintenance unit. To suppress the drop in throughput and increased ink consumption as a result of performing the regular flushing operation at a regular time interval, JP-A-H11-192729 controls flushing according to the printed content so that flushing is not performed more than necessary. For example, when multiple copies of the same content are printed, the nozzles that were used to print the previous page are not flushed. The time for which ink was not ejected from the nozzles is also measured, and only those nozzles for which the measured time exceeds a reference value are flushed.
Various methods are thus used for flushing, and each method has its advantages and disadvantages. For example, regular flushing does not adversely affect print quality, but contributes to a drop in throughput. Furthermore, while the drop in throughput caused by regular flushing can be reduced by the control method described in JP-A-H11-192729, it cannot be completely eliminated. On the other hand, because the onto-paper flushing method can be used parallel the printing operation, it does not contribute to a drop in throughput. However, because ink is discharged onto the printing paper, the flush onto paper method contributes to a drop in print quality.
Some printers also have print modes such as a throughput-priority mode (a so-called “fast mode”) that prioritizes shortening the required printing time, and a print quality-priority mode (a so-called “clean mode”) that prioritizes maintaining print quality. The desirable flushing mode differs according to the print mode in these printers.
When print conditions such as the print speed and print resolution can be set in multiple levels, the desirable flushing method also differs according to the print conditions. Applying the appropriate flushing method according to the print mode or print conditions is therefore desirable.